A multimedia system is designed to present various multimedia materials in various combinations of text, graphics, video, image, animation, sound, etc. Such a system is a combination of hardware and software. The hardware includes a personal computer to which various multimedia devices can be attached. The hardware runs under the control of an operating system and multimedia application programs.
Multimedia applications impose heavy demands on an operating system to move large amounts of data from device to device, from system memory to a device, or vice-versa, in a continuous, real-time manner. Multimedia systems must support a flexible yet consistent means for transporting these large data objects, and control this activity accurately in real time.
The ability to synchronize events is critical to successful multimedia application execution. For example, the application author may decide to display a certain bitmap (e.g. an image of fireworks bursting) at precisely the same time as an audio waveform is played (e.g. a specific cymbals crash during the "Star Spangled Banner"). From a standard OS/2 application perspective, these events might be controlled by two independent threads, or by a single thread, but there is no way for either of these approaches to guarantee that both events will occur within, say, 6 msec of each other. If there is a time delay of 100 msec between events, the user may or may not notice the events are not quite synchronized. If the delay exceeds 500 msec the user will definitely notice the loss of synchronization.
Multimedia extensions for an operating system such as IBM OS/2, Version 2.0 operating system, need to provide the capability of synchronizing two or more data streams (i.e. audio data streams with video data streams). This requires that the mechanism for doing this must be consistent and generalized across a wide variety of multimedia devices as well as data types. The mechanism must be independent of any specific device operations and flexible in synchronization granularity within the limitations of the specific hardware device involved.